It's All About The Patrons!
Added 2022-10-28 14:25:54 +0000 UTCYes, after the better part of a week of work the public premiere of my Deep Dive into the Conn Strobotuner has fallen to the bottom of the pool right off the bat. So, as I expected if I put out one of these a week it will be entirely up to You - my existing Patrons - to keep the channel on the air, because the general subscribership are not going to watch this kind of content. But as long as I have your support I will keep doing it!
Comments
There is a bit more deep deep deepness in the Strobotuner story. The original big black box with the 12 disks all whirling at once was built on the technology that makes the Hammond B-3 sound like it does. The 12 strobodisks and the tone wheels in a Hammond tone generator are all driven with a gear train from a single motor. The speed of that motor sets the frequency to make Concert A 440 Hz, or whatever number you want. All the other wheels are driven via gear train that makes the other wheels turn at the right speed for their particular note. The teeth on a tone wheel (or the pattern on the strobodisk) can also effectively participate in the gear ratios, but the most important point is that any gear train can ONLY generate RATIONAL ratios. This matters because perfect equal temperament uses the 12th root of 2 as the size of every half-step. So the tuning of a B-3 isn’t perfectly equal. Again, this matters when mixtures of intervals are sounded, either in chords, but also for stop voices having non-octave-related partials, like a third, forth, or fifth. The “brown box” strobotuner uses a motor driven by an oscillator which shifts frequency for each note, so it can indeed be tuned to any temperament you want to use, but obviously, out of the box, it does equal temperament. The rings on the strobodisk are division by powers of 2 so it can tune multiple octaves of the same note, but the tuning of that note is set by the 12 tuning coils selected by the root note selector. Today in digital instruments, we still have a version of the problem - approximating the 12th root of two with simple arithmetic done with finite length numbers - but the numbers can be big enough that the pitch error can be reduced below the threshold of (most?) human hearing. Back to the giant 12-eyed Strobotron. My mother had a Baldwin Theatre Organ which, as was common at the time of its genesis, had a set of 12 “top octave oscillators”, each one producing the signal of the highest version of one of the 12 notes. Also on the same card was a set of divide-by-2 flip-flops which produced the lower octaves of that particular pitch. So each circuit card made all the octaves of a single pitch of the top octave scale. Each oscillator was slug-tuned paired with a selected capacitor. Time and the lack of a service tech in less than 200 miles, the organ slowly crept out of tune, finally reaching the point where it was painfully obvious, or obviously painful, and “something must be done”. I borrowed the 12-eyed Strobotron over a holiday break and did the obvious tuning job of putting the top octave oscillators trued up with the appropriate strobodisk. Then came the revelation. When I got it all back together and mom sat down to play some tunes, it was clear that *something* was wrong, but characterizing the “what” was very difficult. It didn’t sound out of tune, per se, but it sure sounded different. Sometimes not much, other times what clearly different. The most aggressive differences were heard in the “mixture” stops. They nominally simulate an ensemble of stops like a brass or wind section playing several parts harmonically. It took a lot of pondering to some up with a theory as to what might be at the root of the problem (ugh!). Time passed, and in the interim, the HS Band Department go one of the new “brown box” Strobotuners. It was sold based on dramatically improved mobility but no mention was made about tuning matters. I borrowed the new “brown box” tuner and over the weekend I retuned the top octave oscillators based on their brown box and it’s note selector switch. When I got it back together and mom played the previous material, the difference was quite clear. The voicing of the Baldwin was very smooth and creamy, while it would be unlikely to find many people who would describe the Hammond B3 that same way. More like “gut bucket” and “screaming”. The fact that tuning the Baldwin essentially by using a B3 as the reference would produce such a dramatic change in the sonority of the instrument was certainly surprising at first, but upon reflection, shows the impact that tuning systems have on instrumentation and the resulting music performance. After retuning, there were still some differences, but they were overall quite small, but putting it back as it was before age related degeneration would require a Baldwin tuning standard, whatever that might be. It was a merry chase, and I learned a bunch about something which was supposed to matter, but I had never hear a real, live example that was utterly compelling.
Mike O'Dell
2022-11-09 04:41:54 +0000 UTCI enjoyed every minute - this is the stuff I like covered and the way you do it.
Donald J Arndt
2022-10-30 23:44:30 +0000 UTC
